Infrastructure, such as roadways, bridges, and water and energy distribution systems are necessary elements of a society and its economy. Like all physical objects that are in continuous use, infrastructure requires periodic maintenance and replacement. The present invention relates to transportation infrastructure that is implemented using a system of conduits and pipes. As used herein, the terms “pipe” and “conduit” are used interchangeably.
Pipeline systems are widely used to transport water, sewage, petroleum products and other materials that can be reduced to a flowable form. Pipeline distribution is efficient and when placed underground, does not interfere with surface use of the same land nor does it detract from the esthetic appeal of the land.
Because most pipelines are buried underground or concealed in some way, they are difficult to reach. Moreover, pipelines that are used to carry municipal services, such as water and sewage, or commercial products such as petroleum, tend to be very large in diameter and can be many miles in length. Thus, removing and replacing pipes in such systems is time consuming and expensive. While these types of pipeline systems are designed to have a long service life, they eventually do require maintenance.
Many pipeline systems are deployed over long distances and form a distribution highway for flowable materials of all kinds. Other pipeline systems are more local in nature, such as the plumbing system in one's home.
During their operation, pipelines tend to be susceptible to a buildup of undesirable deposits along their interior walls. The buildup can be formed from the material being carried by the pipeline or from byproducts created during the transport process. As the buildup continues, the bore or opening within the pipes that form the pipeline, progressively narrows resulting in a reduction in material flow over time and increased pressure within the pipe. If remedial measures are not taken, the bore will eventually close preventing all flow.
Sewage pipelines are particularly susceptible to a buildup of deposits along their inner walls from the sewage they carry and from sewage byproducts. Pipes that carry municipal drinking water also are not immune from a buildup of deposits in the form of, for example, iron and scale.
Petroleum pipelines are notorious for a buildup of paraffin along their inner walls.
In addition to restricted flow and ultimately clogging, a buildup of deposits along the inner walls of a pipeline can be particularly troublesome when portions of the pipe are subjected to wide variations in temperature.
The theory of thermal expansion holds that matter has a tendency to change in volume in response to a change in temperature. As the temperature of matter increases, so does its volume. Correspondingly, a matter's volume decreases as its temperature decreases. The degree of expansion or contraction, divided by the change in temperature, is known as a material's coefficient of thermal expansion.
The wall thickness of a pipe at a particular cross-section factors into the radial temperature gradient of the pipe at that particular cross-section. Thus, a pipe that has a thicker wall thickness at one cross-section due to a buildup of deposits has a different temperature gradient than the temperature gradient at a cross-section having a lesser buildup and thus smaller wall thickness.
Therefore, small temperature variances will be present along the pipeline corresponding to the relative changes in wall thickness due to the variations in deposit thickness built up along the pipe.
Were the inner walls of a pipeline pristine and not subject to a buildup of deposits, its coefficient of thermal expansion along its entire length would be constant, assuming that the temperature of the material carried by the pipeline and the temperature surrounding the pipe remains constant.
However, the buildup of deposits along its inner wall distorts continuity of the coefficient of thermal expansion due to the difference temperature gradients at different points along the pipeline. The discontinuity in expansion rates make the pipeline more susceptible to cracking and breaking at the points of discontinuity, especially when the pipe is under high pressure.
The increased risk of pipeline failure due to cracks and fractures caused by temperature variations is another reason to be concerned with the buildup of deposits along the inner walls of a pipeline.
The reduction in material flow in a pipeline due to the buildup of deposits along the inner wall of the pipes can only be reversed by (1) replacing the affected pipes; (2) increasing the pressure used to force the material through the pipeline; and/or (3) removing the deposit buildup from the pipes that form along their interior walls.
While increased material flow pressure can be an effective short term solution, it will not ameliorate or eliminate the buildup. Moreover, increased pressure places additional stress on the pipeline, increasing the risk of failure and the need for earlier replacement.
The prior art is aware of a number of methods and devices that are used to clean and remove deposits from the inner wall of pipes. These methods include various chemicals and flushes, many of which are name brands that are well known to home owners for maintenance of plumbing systems that are prone to clog. While chemical treatments are useful in some situations, they are not a complete solution due to toxicity and limited effectiveness.
Exposing the inner wall of pipes to certain forms of bacteria has also proved effective in some situations. Mechanical devices such as plungers, mechanical snakes and augers are popular for clearing a clogged pipe in the home. These devices have little utility for removing all contaminates and residue from the interior wall of a pipe but can suffice to at least temporarily open a clogged pipe.
Pipeline systems for commercial use, such as petroleum, water distribution, and sewage recovery, present a more substantial challenge and typically require a more robust approach than that required by a home owner.
High pressure water jetting, pipeline pigs, ultrasonic sound blasts, mechanical rotary drilling and hydro blasting are often used to clean commercial pipeline systems.
As known in the art, a pipeline pig is formed of a body having a diameter and outer circumference that closely matches the inner circumference of the pipe. The pig is forced through the pipe by fluid pressure or by the use of a cable and winch system. As the pig travels through the pipe, it scrapes the deposits from the interior wall of the pipe and transports these deposits along the pipeline.
In order to perform its function, the pig must be substantially rigid in order to scrape deposits from the wall of the pipe, but the pig must also be somewhat compressible in order to pass by intended restrictions in the internal pipe cross-section or obstructions that may be present in the pipe.
In some embodiments, the exterior surface of a pipeline pig is formed of a plastic material, such as polyurethane. A disadvantage of these pigs is that the build-up of paraffin or other material inside the pipe may be so rigid that the pig will compress and ride over the build-up, which results in insufficient cleaning.
Normally, the fluid pressure for propelling the pig through the pipe is supplied by water or other liquids which are injected into the pipe at high pressure.
It is also known in the prior art to initially inject high pressure water behind the pig and to then discontinue the injection of water followed by an inert gas to complete propulsion of the pig through the pipe.
As its name implies, mechanical rotary drilling uses a drill bore of the approximate original interior diameter of the pipe to bore out interior wall buildup.
Ultrasonic sound blasts rely on a focused beam of sound as the blast element to remove the residue buildup.
In hydro blasting, a focused high pressure stream of water, or other fluid, is used to remove the residue buildup.
All of the above-mentioned prior methods and devices suffer from one or more disadvantages when one considers the wide variety of currently installed pipeline system layouts and geometries.
Removable of the buildup of undesirable residue from the interior walls of pipes is not the only maintenance challenge.
The interior walls of pipes in many pipeline systems are coated with a lining having qualities that enhance the flow of the pipeline produce through the pipeline. The lining might also help to seal the pipeline from leaks.
Over time, the wearing effect due to friction of the product constantly rubbing against the interior walls as it moves through the pipes will gradually cause the lining to wear away. From time-to-time, the lining must be replaced. Doing so often is expensive and time consuming.
As illustrated in FIG. 1, transport pipeline systems typically are buried 6 to 8 feet below the surface with only an inlet, one or more inspections ports, and an outlet accessible above ground. FIG. 1 illustrated a simple transport pipeline system. FIG. 2 is a further illustration of transport pipeline system showing that the depth of the pipeline is not consistent as natural terrain will vary from place to place as well as obstructions will often be in the way and must be avoided.
FIG. 3 is a more realistic diagrammatic top view of a modern pipeline system that might be used to carry petroleum from a refinery to customers in difference parts of the country. In fact, most oil and gas is carried across country by pipeline.
FIG. 4 illustrates limitations common among currently available cleaning and lining systems and application methods for pipeline systems. As FIG. 4 shows, access to the pipe line must be gained at a location which will provide a straight run for typical self-propelled or winch-pulled tool, such as the pig described above. All fittings 22-90 degrees are routinely removed to allow tool insertion and lining. In addition, most prior art tools operate in straight pipe segments and can't access vertical portions of the pipeline system, making additional excavations and tool set-ups necessary.
The present invention solves the above noted problems with prior art approaches to cleaning and the replacement of linings in the pipes used in pipeline systems.